There is a HotFix for IBM Domino 9.0.1 FP9 which resolves the following Issue:
SPR TDOOAREP8W Performance issue with long held lock after update to Domino 9.0.1 FP9
This can even result in a hang during the “updall” task.
So, if you have this issue, go ahead and open a PMR and you should get a HotFix which resolves this.